It is essential in clinical medicine to develop a simple and accurate analytical method for detecting nitric oxide (NO) in blood or other body fluid. In order to overcome the shortcomings of previous methods, this experiment developed a novel indirect analytical method of NO in serum.After nitrate was reduced by copper-coated cadmium granules, the nitrite produced was determined by diazotization of fuchsin acid and coupling to resorcinol. The maximum absorption appeared at 436nm, with which the concentration of NO can be determined indirectly.NO concentration and absorbance were linearly correlated over the concentration ranging from 0 to 198μmol/l, r=0.999. The CVs were 7.16% for within-run and 9.07% for between-run assays, respectively. The average recovery rate ranged from 90.6% to 105.2%. The mean concentration of NO 3 − /NO 2 − was 59.2±17.0μmol/l in serum of 30 normal volunteers. The serum concentration of NO 3 − /NO 2 − decreased significantly in patients with congestive heart failure (CHF) compared to the normal volunteers, P<0.05.This method offers a reliable, simple, reagent safe and inexpensive analytical platform for the determination of NO in serum. Using this approach, we determined that the synthesis of endogenous NO decreased in patients with CHF.